The Triple Constraint

Ah, the triple constraint, the cornerstone of project management and project management (PM) lingo. Along the way, I will try to cover the most common acronyms and lingo that are used in the discipline. I neither intend to promote nor condone any particular use, or in many cases, overuse, of project management lingo. My goal is to create familiarity with the terms as they are commonly used in practice.

The triple constraint refers to the three inputs that govern the ability to deliver a project. The three commonly agreed upon constraints are budget, time, and scope. They are often drawn in a triangular shape to represent the relationship between them. This triangular arrangement helps to represent that any adjustment to one of these factors will have an impact on the other two. This relationship will become clearer with examples. Let’s start with definitions:

Budget – the allowed funds (money) that can be used to complete the project. This includes all sub-categories that which money can be spent to complete the project. The most common resources are materials and human capital. In construction, the budget might be constrained on physical building materials. In software engineering it is most often spent on human capital (i.e. software developers) and is generically referred to as resources. Many projects will use a combination of physical materials and human resources.

Time – strictly speaking this is the amount of time needed to complete the work. This can be provided either as a deadline (time-constrained) or can be developed as a duration (calculated based on scope and available resources.) Very often in the corporate environment, the project manager is given a deadline by which the project needs to be delivered. In this common case, the project manager (PM) will work ‘backwards’ from the deadline to complete the project, which is often troublesome for many reasons which will be explained in later posts.

Scope – this is merely what needs to be delivered. Alternatively this can be described as scope of work, the deliverable,a product or requirements. The final project can deliver something tangible such as a building, computer software or designs to build a new line of clothing. Or, at the completion of the project completion there may be something intangible such as new processes for patient protocol in a doctor’s office.

In its simplest form, these three factors govern all that the project manager does. Through the relationships of budget, timeline and scope the project will be executed. The finesse and skill of the project manager to properly manage the relationship inherit to the triple constraint will greatly influence the outcome of the project.

I’ve seen The Triple Constraint in various forms over the years but in my opinion it hides three VERY important constraints on a project:

1. Expert resource availability

Although The Triple Constraint includes resources under costs, it does not focus on the availability of those resources. This is especially critical where there are only a small number of resources available with the specific expertise required and there are multiple projects fighting for those experts.

2. Quality

Once again The Triple Constraint loosely includes quality under scope but this defocusses this constraint and leads to perception such as “its ok if we just add this one extra feature, we can steal some time from testing at the end of the project.”

3. Risks

Risks are not included in any of the categories under The Triple Constraint but can have the biggest impact on the outcome of a project. Without early identification of potential risks and pro-active management of those risks the project is likely to fail.

I completely agree with you. The triple constraint doesn’t represent nearly all that is important in measuring a project. In my opinion, the triple constraint is best used as a communication and negotiation tool with your stakeholders. If provides a framework to explain how things work and what needs to be changed. But a skilled project manager uses many more tools during the process of executing a project that you have pointed out are not contained in the triple constraint.

There is not a single picture, model, or scenario that describes all of project management. It is a complex web of managing many different aspects including the ones you have mentioned above. I do think the first two you mention are inherently captured in the triple constraint and the savvy project manager will bring them to the forefront.

Expert Resource Availability: true this is technically a subset of Budget. But as we both know, warm bodies does not equal a successful project. Extra testers do not make up for a shortage of developers. So what I do when I have a new set of stakeholders for a project I define what the acceptable parameters. Resources are not all equal and less skilled or shortage of resources will increase time and likely reduce quality.

Quality: I agree with you here as well and a point that I failed to bring up in the article is that if one aspect of your triangle changes and you fail to adjust the other two in response you will face quality issues.

Risks: once of my personal favorite components, although I feel it is a separate discipline concept from the triple constraint in the PM Toolkit is risk management. To me it is not something that defines the project (which the triple constraint heps to do) but instead it is something that needs to be actively managed throughout the project. For all large project I always maintain a top 5 Risks and Issues list that stakeholders are aware of at all times (obviously were are managing a larger total list of risks and issues in the background. Definitely a future topic.